Propylene polymers incorporating polyethylene macromers

ABSTRACT

A polyolefin product is provided which comprises a branched olefin copolymer having an isotactic polypropylene backbone, polyethylene branches and, optionally, one or more comonomers. The total comonomer content of the branched olefin copolymer is from 0 to 20 mole percent. Also, the mass ratio of the isotactic polypropylene to the polyethylene ranges from 99.9:0.1 to 50:50. Additionally, a process is provided for preparing a branched olefin copolymer which comprises:  
     a) copolymerizing ethylene, optionally with one or more copolymerizable monomers, in a polymerization reaction under conditions sufficient to form copolymer having greater than 40% chain end-group unsaturation;  
     b) copolymerizing the product of a) with propylene and, optionally, one or more copolymerizable monomers, in a polymerization reactor under suitable polypropylene polymerization conditions using a chiral, stereorigid transition metal catalyst capable of producing isotactic polypropylene; and  
     c) recovering a branched olefin copolymer.

[0001] This document is a Divisional of Ser. No. 09/020,307, filingdate, Feb. 6, 1998; application Ser. No. 09/020,307 is based on U.S.Provisional Application Nos. 60/037,323, filed Feb. 7, 1997, 60/046,812,filed May 2, 1997, and 60/067,782, filed Dec. 10, 1997.

FIELD OF THE INVENTION

[0002] The present invention relates to propylene polymers incorporatingmacromers and a method for the preparation of branched polypropyleneutilizing chiral, stereorigid transition metal catalyst compounds.

BACKGROUND OF THE INVENTION

[0003] Polypropylene and related polymers are known to have low meltstrength. This is a significant deficiency in key application areas suchas thermoforming, blow molding, and fiber spinning. Polyethylene on theother hand is used extensively in blown film applications requiring goodmelt strength. The limitations in the melt strength of polypropylenesshow up as excess sag in sheet extrusion, rapid thinning of walls inparts thermoformed in the melt phase, low draw-down ratios in extrusioncoating, poor bubble formation in extrusion foam materials, and relativeweakness in large-part blow molding. Thus, it would be highly desirableto produce polypropylene and related polymers having enhanced meltstrength as well as commercially valuable processability.

[0004] Increasing the melt strength of polymers such as polypropylenehas been an industrial goal for well over ten years, however, successhas been limited. The desirable properties that have made low densitypolyethylene commercially successful are attributed in large part tohigh melt strength and excellent processability. Both of theseproperties are attributed to the presence of long chain branching whichis thought to occur under high pressure polymerization conditions.

[0005] There has been some success in increasing the melt strength ofpolypropylene. For example, EP 190 889 A2 discloses high energyirradiation of polypropylene to create what is believed to bepolypropylene having substantial free-end long branches of propyleneunits. EP 384 431 discloses the use of peroxide decomposition ofpolypropylene in the substantial absence of oxygen to obtain a similarproduct.

[0006] Other attempts to improve the melt properties of polypropyleneinclude U.S. Pat. No. 5,541,236, which introduces long chain branchingby bridging two PP backbones to form H-type polymers, and U.S. Pat. No.5,514,761, which uses dienes incorporated in the backbones to achieve asimilar effect. However, it is difficult to avoid cross-linking and gelformation in such processes.

[0007] Thus, there is still a need for propylene polymers havingimproved melt strength and good processability.

SUMMARY OF THE INVENTION

[0008] The present invention meets that need by providing a polyolefinproduct which comprises a branched olefin copolymer having an isotacticpolypropylene backbone, polyethylene branches and, optionally, one ormore comonomers. The total comonomer content of the branched olefincopolymer is from 0 to 20 mole percent. Also, the mass ratio of theisotactic polypropylene to the polyethylene ranges from 99.9:0.1 to50:50. Additionally, a process is provided for preparing a branchedolefin copolymer which comprises:

[0009] a) copolymerizing ethylene, optionally with one or morecopolymerizable monomers, in a polymerization reaction under conditionssufficient to form copolymer having greater than 40% chain end-groupunsaturation;

[0010] b) copolymerizing the product of a) with propylene and,optionally, one or more copolymerizable monomers, in a polymerizationreactor under suitable polypropylene polymerization conditions using achiral, stereorigid transition metal catalyst capable of producingisotactic polypropylene; and

[0011] c) recovering a branched olefin copolymer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a graphic illustration of the GPC-FTIR data for thepolymer produced in Example 4.

[0013]FIG. 2 is a graphic illustration of the complex viscosity vs.shear rate curve for the polymer products produced in Example 5 andComparative Example 7.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The polyolefin compositions of this invention are comprised ofbranched polymers wherein the polymer backbone is derived from propyleneand the polymer branches are derived from polyethylene. The branches andbackbone are polymerized under coordination or insertion conditions withactivated transition metal organometallic catalyst compounds. Thebranches are composed of polyethylene which may exhibit crystalline,semi-crystalline or glassy properties suitable for hard phase domains inaccordance with the art understood meaning of those terms, and areattached to a polymeric backbone that may also be crystalline. Thebackbone is composed of stereospecific polypropylene and, optionally,one or more comonomers. In addition, the backbone has a melt point of80° C. or higher. Preferably, the backbone is isotactic polypropylene.These compositions are useful as thermoforming resins and exhibitimproved processability over current polypropylene compositions.

[0015] In the branched olefin copolymer of the present invention, themass ratio of the isotactic polypropylene to the polyethylene rangesfrom 99.9:0.1 to 50:50. Preferably, the mass ratio of the isotacticpolypropylene to the polyethylene ranges from 95:5 to 50:50.

[0016] As used herein, “isotactic polypropylene” is defined as having atleast 70% isotactic pentads according to analysis by ¹³C-NMR. “Highlyisotactic polypropylene” is defined as having at least 90% isotacticpentads according to analysis by ¹³C-NMR. “Syndiotactic polypropylene”is defined as polypropylene having at least 70% syndiotactic pentadsaccording to analysis by ¹³C-NMR. Preferably, the backbone of thepresent invention is highly isotactic polypropylene.

[0017] The Macromer Sidechains

[0018] The branches of the polymer (also referred to as “sidechains”)are comprised ethylene and, optionally, one or more comonomers.Preferably, the comonomers are chemical units capable of formingcrystalline or glassy polymeric segments under conditions of insertionpolymerization. Suitable comonomers include C₃-C₂₀ α-olefins, geminallydisubstituted monomers, C₅-C₂₅ cyclic olefins, C₈-C₂₅ styrenic olefinsand lower carbon number (C₃-C₈) alkyl-substituted analogs of the cyclicand styrenic olefins. Thus, typically, the branches can comprise from85-100 mol % ethylene, and from 0-15 mol % comonomer, preferably 90-99mol % ethylene and 1-10 mol % comonomer, most preferably 94-98 mol %ethylene and 2-6 mol % comonomer. In particular, as the sidechain Mnincreases above about 3,000, it is preferable to introduce small amountsof comonomer to minimize embrittlement, e.g., about 0.2-4.0 mol. %comonomer. The selection of comonomer can be based upon properties otherthan crystallinity disrupting capability, for instance, a longer olefincomonomer, such as 1-octene, may be preferred over a shorter olefin suchas 1-butene for improved polyethylene film tear. For improvedpolyethylene film elasticity or barrier properties, a cyclic comonomersuch as norbornene or alkyl-substituted norbornene may be preferred overan α-olefin.

[0019] The sidechains can have narrow or broad molecular weightdistribution (Mw/Mn), for example, from 1.1 to 30, typically 2-8.Additionally, the sidechains can have different comonomer compositions,e.g., including the orthogonal compositional distributions described inU.S. Pat. No. 5,382,630 (CDBI>50%), incorporated by reference forpurposes of U.S. patent practice. Optionally, mixtures of sidechainswith different molecular weights and/or compositions may be used.

[0020] The M_(n) of the sidechains are within the range of from greaterthan or equal to 500 and less than or equal to 45,000. Preferably theM_(n) of the sidechains is from 1500 to 30,000, and more preferably theM_(n) is from 1500 to 25,000. A preferred branched olefinic copolymerwithin this class will have a melt enthalpy (ΔH_(m)) as measured bydifferential scanning calorimetry of ≦90 cal/g (measured by integratingheat flows recorded at temperatures ≧80° C. while scanning at ≧5°C./min).

[0021] Conditions sufficient to form the sidechain copolymer includeusing suitable ethylene and comonomer reactant ratios to assure thedescribed sidechain olefin-derived unit constitution, plus catalyst andprocess conditions conducive to forming the unsaturated chain ends. Theteachings of copending provisional application U.S. Ser. No. 60/037,323filed Feb. 7, 1997 are specific to suitable catalyst selection and useto prepare macromeric copolymer chains with a high yield of vinylunsaturation. The metallocene catalyst used in the step a) preparationof the unsaturation-containing macromer can be essentially any catalystcapable of insertion polymerization of ethylene, it can be one capableof high comonomer incorporation capability (see below) or of lowcomonomer incorporation capability. Those of low incorporationcapability are typically those that are more congested at the metalcoordination site, thus unbridged and substituted unbridged metallocenecatalysts are particularly suitable. See also the teachings of U.S. Pat.No. 5,498,809 and international publications WO 94/19436 and WO94/13715, describing means of preparing vinylidene-terminatedethylene-1-butene copolymers in high yields. See also, the teachings ofcopending application U.S. Ser. No. 08/651,030, filed May 21, 1996, asto the preparation of ethylene-isobutylene copolymers having high levelsof vinylidene chain-end unsaturation. Throughout the description above,and below, the phrase “chain-end” or “terminal” when referring tounsaturation means olefin unsaturation suitable for insertionpolymerization whether or not located precisely at the terminus of achain. All documents of this paragraph are incorporated by reference forpurposes of U.S. patent practice.

[0022] In a particular embodiment, polymeric unsaturation-containingmacromer product suitable as branches for a subsequent copolymerizationreaction can be prepared under solution polymerization conditions withpreferred molar ratios of aluminum in the alkyl alumoxane activator,e.g., methyl alumoxane (MAO), to transition metal. Preferably that levelis ≧20 and =175; more preferably ≧20 and =140; and, most preferably ≧20and =100. The temperature, pressure and time of reaction depend upon theselected process but are generally within the normal ranges for asolution process. Thus temperatures can range from 20° C. to 200° C.,preferably from 30° C. to 150° C., more preferably from 50° C. to 140°C., and most preferably between 55° C. and 135° C. The pressures of thereaction generally can vary from atmospheric to 345 MPa, preferably to182 MPa. For typical solution reactions, temperatures will typicallyrange from ambient to 250° C. with pressures from ambient to 3.45 MPa.The reactions can be run batchwise. Conditions for suitable slurry-typereactions are similar to solution conditions except reactiontemperatures are limited to those below the melt temperature of thepolymer. In an additional, alternative reaction configuration, asupercritical fluid medium can be used with temperatures up to 250° C.and pressures up to 345 MPa. Under high temperature and pressurereaction conditions, macromer product of lower molecular weight rangesare typically produced, e.g., M_(n) about 1,500.

[0023] Suitable catalyst compounds that when activated can achieve highchain-end unsaturations specifically include those identified above withrespect to the preparation of high vinyl or vinylidene-containingmacromers. Catalyst compounds which are suitable for preparing thebranched olefin copolymer of the present invention are discussed in moredetailed below.

[0024] The polypropylene macromers can have narrow or broad molecularweight distribution (Mw/Mn), for example, from 1.5 to 5, typically 1.7to 3. Optionally, mixtures of sidechains with different molecularweights may be used.

[0025] Preferably, the macromers of the present invention are made usingsolution-phase conditions. Preferred solvents for solution phasereactions are selected on the basis of polymer solubility, volatilityand safety/health considerations. Non-polar alkanes or aromatics arepreferred.

[0026] The Polyolefin Backbone

[0027] The polyolefin backbone of the present invention is composed ofpropylene monomers and, optionally, one or more comonomers. In oneembodiment of the present invention, no comonomers are present in thepolyolefin backbone, resulting in a polymer having an isotacticpolypropylene backbone and polyethylene sidechains.

[0028] In another embodiment of the present invention, one or morecomonomers are present in the backbone. Comonomers which are useful inthe present invention include ethylene, C₄-C₂₀ α-olefins, and lowercarbon number (C₃-C₈) alkyl substituted analogs of the cyclic andstyrenic olefins. Other copolymerizable monomers include geminallydisubstituted olefins such as isobutylene, C₅-C₂₅ cyclic olefins such ascyclopentene, norbornene and alkyl-substituted norbornenes, and styrenicmonomers such as styrene and alkyl substituted styrenes. Comonomers areselected for use based on the desired properties of the polymer productand the metallocene employed will be selected for its ability toincorporate the desired amount of olefins.

[0029] When comonomers are used, they preferably comprise from 3 to 20mole percent of the branched olefin copolymer. More preferably, thecomonomers comprise from 5 to 17 mole percent of the branched olefincopolymer.

[0030] In another embodiment of the present invention, the backbone ofthe present invention contains syndiotactic polypropylene and,optionally, one or more comonomers. Essentially all of the backbone canbe syndiotactic, resulting in a polymer having a syndiotacticpolypropylene backbone and polyethylene sidechains. Alternatively, thebackbone can be a combination of syndiotactic and isotacticpolypropylene with, optionally, one or more comonomers.

[0031] The mass of the backbone will typically comprise at least 40 wt %of the total polymer mass, that of the backbone and the sidechainstogether, so the backbone typically will have a nominal weight-averagemolecular weight (M_(w)) weight of at least equal to or greater thanabout 60,000. The term nominal is used to indicate that directmeasurement of M_(w) of the backbone is largely impossible but thatcharacterization of the copolymer product will exhibit measurements ofM_(w) that correlate to a close approximate weight of the polymericbackbone inclusive only of the monoolefin mer derivatives and theinsertion moieties of the sidebranches when the macromer consists ofless than 50% of the total polymer mass.

[0032] Catalysts

[0033] Catalysts which are useful for producing the branched polyolefinof the present invention include all catalysts which are capable ofproducing isotactic polypropylene and incorporating significantquantities of the isotactic polyethylene macromers of the presentinvention. Preferably, metallocene catalysts are used.

[0034] As used herein “metallocene” refers generally to compoundsrepresented by the formula Cp_(m)MR_(n)X_(q) wherein Cp is acyclopentadienyl ring which may be substituted, or derivative thereofwhich may be substituted, M is a Group 4, 5, or 6 transition metal, forexample titanium, zirconium, hafnium, vanadium, niobium, tantalum,chromium, molybdenum and tungsten, R is a hydrocarbyl group orhydrocarboxy group having from one to 20 carbon atoms, X is a halogen,and m=1-3, n=0-3, q=0-3, and the sum of m+n+q is equal to the oxidationstate of the transition metal.

[0035] Methods for making and using metallocenes are well known in theart. For example, metallocenes are detailed in U.S. Pat. Nos. 4,530,914;4,542,199; 4,769,910; 4,808,561; 4,871,705; 4,933,403; 4,937,299;5,017,714; 5,057,475; 5,120,867; 5,278,119; 5,304,614; 5,324,800;5,350,723; 5,391,790; and 5,635,573 each fully incorporated herein byreference.

[0036] Preferred metallocenes are those that are stereorigid andcomprise a Group 4, 5, or 6 transition metal, biscyclopentadienylderivative, preferably bis-indenyl metallocene components having thefollowing general structure:

[0037] wherein M¹ is a metal of Group 4, 5, or 6 of the Periodic Table,for example titanium, zirconium, hafnium, vanadium, niobium, tantalum,chromium, molybdenum and tungsten, preferably, zirconium, hafnium andtitanium, most preferably zirconium and hafnium;

[0038] R¹ and R² are identical or different, are one of a hydrogen atom,a C₁-C₁₀ alkyl group, preferably a C₁-C₃ alkyl group, a C₁-C₁₀ alkoxygroup, preferably a C₁-C₃ alkoxy group, a C₆-C₁₀ aryl group, preferablya C₆-C₈ aryl group, a C₆-C₁₀ aryloxy group, preferably a C₆-C₉ aryloxygroup, a C₂-C₁₀ alkenyl group, preferably a C₂-C₄ alkenyl group, aC₇-C₄₀ arylalkyl group, preferably a C₇-C₁₀ arylalkyl group, a C₇-C₄₀alkylaryl group, preferably a C₇-C₁₂ alkylaryl group, a C₈-C₄₀arylalkenyl group, preferably a C₉-C₁₂ arylalkenyl group, or a halogenatom, preferably chlorine;

[0039] R³ and R⁴ are hydrogen atoms;

[0040] R⁵ and R⁶ are identical or different, preferably identical, areone of a hydrogen atom, halogen atom, preferably a fluorine, chlorine orbromine atom, a C₁-C₁₀ alkyl group, preferably a C₁-C₄ alkyl group,which may be halogenated, a C₆-C₁₀ aryl group, which may be halogenated,preferably a C₆-C₈ aryl group, a C₂-C₁₀ alkenyl group, preferably aC₂-C₄ alkenyl group, a C₇-C₄₀-arylalkyl group, preferably a C₇-C₁₀arylalkyl group, a C₇-C₄₀ alkylaryl group, preferably a C₇-C₁₂ alkylarylgroup, a C₈-C₄₀ arylalkenyl group, preferably a C₈-C₁₂ arylalkenylgroup, a —NR₂ ¹⁵, —SR¹⁵, —OR¹⁵, —OSiR₃ ¹⁵ or —PR₂ ¹⁵ radical, whereinR¹⁵ is one of a halogen atom, preferably a chlorine atom, a C₁-C₁₀ alkylgroup, preferably a C₁-C₃ alkyl group, or a C₆-C₁₀ aryl group,preferably a C₆-C₉ aryl group;

[0041] R⁷ is

[0042]  ═BR^(11,)═AlR¹¹, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO₂, ═NR¹¹, ═CO,PR¹¹, or ═P(O)R¹¹;

[0043] wherein:

[0044] R¹¹, R¹² and R¹³ are identical or different and are a hydrogenatom, a halogen atom, a C₁-C₂₀ alkyl group, preferably a C₁-C₁₀ alkylgroup, a C₁-C₂₀ fluoroalkyl group, preferably a C₁-C₁₀ fluoroalkylgroup, a C₆-C₃₀ aryl group, preferably a C₆-C₂₀ aryl group, a C₆-C₃₀fluoroaryl group, preferably a C₆-C₂₀ fluoroaryl group, a C₁-C₂₀ alkoxygroup, preferably a C₁-C₁₀ alkoxy group, a C₂-C₂₀ alkenyl group,preferably a C₂-C₁₀ alkenyl group, a C₇-C₄₀ arylalkyl group, preferablya C₇-C₂₀ arylalkyl group, a C₈-C₄₀ arylalkenyl group, preferably aC₈-C₂₂ arylalkenyl group, a C₇-C₄₀ alkylaryl group, preferably a C₇-C₂₀alkylaryl group or R¹¹ and R¹², or R¹¹ and R¹³, together with the atomsbinding them, can form ring systems;

[0045] M² is silicon, germanium or tin, preferably silicon or germanium,most preferably silicon;

[0046] R⁸ and R⁹ are identical or different and have the meanings statedfor R¹¹;

[0047] m and n are identical or different and are zero, 1 or 2,preferably zero or 1, m plus n being zero, 1 or 2, preferably zero or 1;and

[0048] the radicals R¹⁰ are identical or different and have the meaningsstated for R¹¹, R¹² and R¹³. Two adjacent R¹⁰ radicals can be joinedtogether to form a ring system, preferably a ring system containing fromabout 4-6 carbon atoms.

[0049] Alkyl refers to straight or branched chain substituents. Halogen(halogenated) is fluorine, chlorine, bromine or iodine atoms, preferablyfluorine or chlorine.

[0050] Particularly preferred metallocenes are compounds of thestructures:

[0051] wherein:

[0052] M¹ is Zr or Hf, R¹ and R² are methyl or chlorine, and R⁵, R⁶ R⁸,R⁹, R¹⁰, R¹¹ and R¹² have the above-mentioned meanings.

[0053] The chiral metallocenes may be used as a racemate for thepreparation of highly isotactic polypropylene polymers and copolymers.It is also possible to use the pure R or S form. An optically activepolymer can be prepared with these pure stereoisomeric forms. Preferablythe meso form of the metallocene is removed to ensure the center (i.e.,the metal atom) provides stereoregular polymerization. Separation of thestereoisomers can be accomplished by known literature techniques. Forspecial products it is also possible to use rac/meso mixtures.

[0054] Generally, the metallocenes are prepared by a multi-step processinvolving repeated deprotonations/metallations of the aromatic ligandsand introduction of the bridge and the central atom by their halogenderivatives. The following reaction scheme illustrates this genericapproach:

[0055] Additional methods for preparing metallocenes of the presentinvention are fully described in the Journal of Organometallic Chem.,volume 288, (1958), pages 63-67, and in EP-A-320762, for preparation ofthe metallocenes described, both of which are herein fully incorporatedby reference.

[0056] Illustrative but non-limiting examples of some preferredmetallocenes include: Dimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)ZrCl₂Dimethylsilandiylbis(2-methyl-4,5-benzoindenyl)ZrCl₂;Dimethylsilandiylbis(2-methyl-4,6-diisopropylindenyl)ZrCl₂;Dimethylsilandiylbis(2-ethyl-4-phenyl-1-indenyl)ZrCl₂;Dimethylsilandiylbis (2-ethyl-4-naphthyl-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4-(1-naphthyl)-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4-(2-naphthyl)-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4,5-diisopropyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2,4,6-trimethyl-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl₂,1,2-Ethandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl₂,1,2-Butandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4-isopropyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4-t-butyl-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-4-isopropyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-ethyl-4-methyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2,4-dimethyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-α-acenaphth-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-4,5-(methylbenzo)-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-4,5-(tetramethylbenzo)-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-a-acenaphth-1-indenyl)ZrCl₂,1,2-Ethandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,1,2-Butandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl₂,1,2-Ethandiylbis(2,4,7-trimethyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-1-indenyl)ZrCl₂,1,2-Ethandiylbis(2-methyl-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-1-indenyl)ZrCl₂,Diphenylsilandiylbis(2-methyl-1-indenyl)ZrCl₂,1,2-Butandiylbis(2-methyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-ethyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-5-isobutyl-1-indenyl)ZrCl₂,Phenyl(Methyl)silandiylbis(2-methyl-5-isobutyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2-methyl-5-t-butyl-1-indenyl)ZrCl₂,Dimethylsilandiylbis(2,5,6-trimethyl-1-indenyl)ZrCl₂, and the like.

[0057] Some preferred metallocene catalyst components are described indetail in U.S. Pat. Nos. 5,149,819, 5,243,001, 5,239,022, 5,296,434 and5,276,208 all of which are herein fully incorporated by reference. Inaddition, the bis-amido and bis-arylamido transition metal catalysts ofU.S. Pat. No. 5,318,935 and copending U.S. patent application Ser. No.08/803,687, filed Feb. 24, 1997, and the α-diimine nickel catalystcomplexes of WO 96/23010 can be useful in incorporating the macromers ofthe present invention into the backbone.

[0058] Most preferably, the catalyst used to produce the branchedpolyolefin of the present invention is a dimethylsilyl-bridgedbis-indenyl zirconocene or hafnocene such as dimethylsilylbis(2-methyl-indenyl) ZrCl₂, dimethylsilylbis(2-methyl-4-phenyl-1-indenyl) ZrCl₂, dimethylsilylbis(2-methyl-4-(1-naphthyl)-1-indenyl) ZrCl₂, or dimethylsilylbis(indenyl)hafnium dimethyl.

[0059] Preferably, the catalysts used to produce the syndiotacticpolypropylene backbone of the present invention are those disclosed inU.S. Pat. Nos. 4,892,851, 5,155,080, and 5,132,381, the disclosures ofwhich are hereby incorporated by reference.

[0060] The terms “cocatalyst” and “activator” are used hereininterchangeably and are defined to be any compound or component whichcan activate a bulky ligand transition metal compound or a metallocene,as defined above. Alumoxane may be used as an activator. There are avariety of methods for preparing alumoxane, non-limiting examples ofwhich are described in U.S. Pat. Nos. 4,665,208, 4,952,540, 5,091,352,5,206,199, 5,204,419, 4,874,734, 4,924,018, 4,908,463, 4,968,827,5,308,815, 5,329,032, 5,248,801, 5,235,081, 5,157,137, 5,103,031 andEP-A-0 561 476, EP-B1-0 279 586, EP-A-0 594-218 and WO 94/10180, each ofwhich is fully incorporated herein by reference. It may be preferable touse a visually clear methylalumoxane. A cloudy or gelled alumoxane canbe filtered to produce a clear solution or clear alumoxane can bedecanted from the cloudy solution.

[0061] It is also within the scope of this invention to use ionizingactivators, neutral or ionic, or compounds such as tri(n-butyl)ammoniumtetrakis(pentaflurophenyl)boron, which ionize the neutral metallocenecompound. Such ionizing compounds may contain an active proton, or someother cation associated with but not coordinated or only looselycoordinated to the remaining ion of the ionizing compound. Combinationsof activators are also contemplated by the invention, for example,alumoxane and ionizing activators in combinations, see for example, WO94/07928.

[0062] Descriptions of ionic catalysts for coordination polymerizationcomprised of metallocene cations activated by non-coordinating anionsappear in the early work in EP-A-0 277 003, EP-A-0 277 004 and U.S. Pat.No. 5,198,401 and WO-A-92/00333 (incorporated herein by reference).These teach a preferred method of preparation wherein metallocenes(bisCp and monoCp) are protonated by an anion precursor such that analkyl/hydride group is abstracted from a transition metal to make itboth cationic and charge-balanced by the non-coordinating anion.

[0063] The term “noncoordinating anion” means an anion which either doesnot coordinate to said cation or which is only weakly coordinated tosaid cation thereby remaining sufficiently labile to be displaced by aneutral Lewis base. “Compatible” noncoordinating anions are those whichare not degraded to neutrality when the initially formed complexdecomposes. Further, the anion will not transfer an anionic substituentor fragment to the cation so as to cause it to form a neutral fourcoordinate metallocene compound and a neutral by-product from the anion.Noncoordinating anions useful in accordance with this invention arethose which are compatible, stabilize the metallocene cation in thesense of balancing its ionic charge in a +1 state, yet retain sufficientlability to permit displacement by an ethylenically or acetylenicallyunsaturated monomer during polymerization.

[0064] The use of ionizing ionic compounds not containing an activeproton but capable of producing the both the active metallocene cationand an noncoordinating anion is also known. See, EP-A-0 426 637 andEP-A-0 573 403 (incorporated herein by reference). An additional methodof making the ionic catalysts uses ionizing anion pre-cursors which areinitially neutral Lewis acids but form the cation and anion uponionizing reaction with the metallocene compounds, for example the use oftris(pentafluorophenyl) boron. See EP-A-0 520 732 (incorporated hereinby reference). Ionic catalysts for addition polymerization can also beprepared by oxidation of the metal centers of transition metal compoundsby anion pre-cursors containing metallic oxidizing groups along with theanion groups, see EP-A-0 495 375 (incorporated herein by reference).

[0065] Where the metal ligands include halogen moieties (for example,bis-cyclopentadienyl zirconium dichloride) which are not capable ofionizing abstraction under standard conditions, they can be convertedvia known alkylation reactions with organometallic compounds such aslithium or aluminum hydrides or alkyls, alkylalumoxanes, Grignardreagents, etc. See EP-A-0 500 944 and EP-A1-0 570 982 (incorporatedherein by reference) for in situ processes describing the reaction ofalkyl aluminum compounds with dihalo-substituted metallocene compoundsprior to or with the addition of activating anionic compounds.

[0066] Support Materials

[0067] The metallocenes described herein are preferably supported usinga porous particulate material, such as for example, talc, inorganicoxides, inorganic chlorides and resinous materials such as polyolefin orpolymeric compounds.

[0068] The most preferred support materials are porous inorganic oxidematerials, which include those from the Periodic Table of Elements ofGroups 2, 3, 4, 5, 13 or 14 metal oxides. Silica, alumina,silica-alumina, and mixtures thereof are particularly preferred. Otherinorganic oxides that may be employed either alone or in combinationwith the silica, alumina or silica-alumina are magnesia, titania,zirconia, and the like.

[0069] Preferably the support material is porous silica which has asurface area in the range of from about 10 to about 700 m²/g, a totalpore volume in the range of from about 0.1 to about 4.0 cc/g and anaverage particle size in the range of from about 10 to about 500 μm.More preferably, the surface area is in the range of from about 50 toabout 500 m²/g, the pore volume is in the range of from about 0.5 toabout 3.5 cc/g and the average particle size is in the range of fromabout 20 to about 200 μm. Most preferably the surface area is in therange of from about 100 to about 400 m²/g, the pore volume is in therange of from about 0.8 to about 3.0 cc/g and the average particle sizeis in the range of from about 30 to about 100 μm. The average pore sizeof typical porous support materials is in the range of from about 10 toabout 1000 Å. Preferably, a support material is used that has an averagepore diameter of from about 50 to about 500 Å, and most preferably fromabout 75 to about 350 Å. It may be particularly desirable to dehydratethe silica at a temperature of from about 100° C. to about 800° C.anywhere from about 3 to about 24 hours.

[0070] The metallocenes, activator and support material may be combinedin any number of ways. Suitable support techniques are described in U.S.Pat. Nos. 4,808,561 and 4,701,432 (each fully incorporated herein byreference.). Preferably the metallocenes and activator are combined andtheir reaction product supported on the porous support material asdescribed in U.S. Pat. No. 5,240,894 and WO 94/28034, WO 96/00243, andWO 96/00245 (each fully incorporated herein by reference.)Alternatively, the metallocenes may be preactivated separately and thencombined with the support material either separately or together. If themetallocenes are separately supported, then preferably, they are driedthen combined as a powder before use in polymerization.

[0071] Regardless of whether the metallocene and activator areseparately precontacted or whether the metallocene and activator arecombined at once, the total volume of reaction solution applied toporous support is preferably less than about 4 times the total porevolume of the porous support, more preferably less than about 3 timesthe total pore volume of the porous support and even more preferably inthe range of from more than about 1 to less than about 2.5 times thetotal pore volume of the porous support. Procedures for measuring thetotal pore volume of porous support are well known in the art. Thepreferred method is described in Volume 1, Experimental Methods inCatalyst Research, Academic Press, 1968, pages 67-96.

[0072] Methods of supporting ionic catalysts comprising metallocenecations and noncoordinating anions are described in WO 91/09882, WO94/03506, WO 96/04319 and U.S. Pat. No. 5,643,847 (incorporated hereinby reference). The methods generally comprise either physical adsorptionon traditional polymeric or inorganic supports that have been largelydehydrated and dehydroxylated, or using neutral anion precursors thatare sufficiently strong Lewis acids to activate retained hydroxy groupsin silica containing inorganic oxide supports such that the Lewis acidbecomes covalently bound and the hydrogen of the hydroxy group isavailable to protonate the metallocene compounds.

[0073] The supported catalyst system may be used directly inpolymerization or the catalyst system may be prepolymerized usingmethods well known in the art. For details regarding prepolymerization,see U.S. Pat. Nos. 4,923,833 and 4,921,825, EP 0 279 863 and EP 0 354893 each of which is fully incorporated herein by reference.

[0074] Polymerization Processes

[0075] The branched polyolefin of the present invention may be producedusing the catalysts described above in any process including gas, slurryor solution phase or high pressure autoclave processes. (As used herein,unless differentiated, “polymerization” includes copolymerization and“monomer” includes comonomer.) Additionally, combinations of the abovereactor types in multiple, series reactors and/or multiple reactionconditions and/or multiple catalyst configurations are explicitlyintended. Preferably, a gas or slurry phase process is used, mostpreferably a bulk liquid propylene polymerization process is used.

[0076] In the preferred embodiment, this invention is directed towardthe bulk liquid polymerization and copolymerization of propylene in aslurry or gas phase polymerization process, particularly a slurrypolymerization process. Another embodiment involves copolymerizationreactions of propylene with one or more comonomers. Such comonomersinclude alpha-olefin monomers having from 4 to 20 carbon atoms,preferably 4-12 carbon atoms, for example alpha-olefin comonomers ofethylene, butene-1, pentene-1,4-methylpentene-1, hexene-1, octene-1,decene-1. Other suitable comonomers include geminally disubstitutedmonomers, C₅-C₂₅ cyclic olefins such as cyclopentene or norbornene,styrenic olefins such as styrene, and lower carbon number (C₃-C₈) alkylsubstituted analogs of the cyclic and styrenic olefins. In addition,comonomers such as polar vinyl, diolefins such as dienes, for example,1,3-butadiene, 1,4-hexadiene, norbornadiene or vinylnorbornene,acetylene and aldehyde monomers are suitable.

[0077] Typically in a gas phase polymerization process a continuouscycle is employed wherein one part of the cycle of a reactor, a cyclinggas stream, otherwise known as a recycle stream or fluidizing medium, isheated in the reactor by the heat of polymerization. The recycle streamusually contains one or more monomers continuously cycled through afluidized bed in the presence of a catalyst under reactive conditions.This heat is removed in another part of the cycle by a cooling systemexternal to the reactor. The recycle stream is withdrawn from thefluidized bed and recycled back into the reactor. Simultaneously,polymer product is withdrawn from the reactor and new or fresh monomeris added to replace the polymerized monomer. (See for example U.S. Pat.Nos. 4,543,399; 4,588,790; 5,028,670; 5,352,749; 5,405,922, and5,436,304 all of which are fully incorporated herein by reference.)

[0078] A slurry polymerization process generally uses pressures in therange of from about 1 to about 500 atmospheres or even greater andtemperatures in the range of from −60° C. to about 280° C. In a slurrypolymerization, a suspension of solid, particulate polymer is formed ina liquid or supercritical polymerization medium to which propylene andcomonomers and often hydrogen along with catalyst are added. The liquidemployed in the polymerization medium can be, for example, an alkane ora cycloalkane. The medium employed should be liquid under the conditionsof polymerization and relatively inert such as hexane and isobutane. Inthe preferred embodiment, propylene serves as the polymerization diluentand the polymerization is carried out using a pressure of from about 200kPa to about 7,000 kPa at a temperature in the range of from about 50°C. to about 120° C.

[0079] The periods of time for each stage will depend upon the catalystsystem, comonomer and reaction conditions. In general, propylene shouldbe homopolymerized for a time period sufficient to yield a compositionhaving from about 10 to about 90 weight percent homopolymer based on thetotal weight of the polymer, preferably from about 20 to about 80 weightpercent, even more preferably from about 30 to about 70 homopolymerweight percent based on the total weight of the polymer.

[0080] The above-described temperatures, reaction times and otherconditions are considered suitable polypropylene polymerizationconditions for the purposes of this invention.

[0081] The polymerization may be conducted in batch or continuous modeand the entire polymerization may take place in one reactor or,preferably, the polymerization may be carried out in a series ofreactors. If reactors in series are used, then the comonomer may beadded to any reactor in the series, however, preferably, the comonomeris added to the second or subsequent reactor.

[0082] Hydrogen may be added to the polymerization system as a molecularweight regulator in the first and/or subsequent reactors depending uponthe particular properties of the product desired and the specificmetallocenes used. When metallocenes having different hydrogen responsesare used, the addition of hydrogen will affect the molecular weightdistribution of the polymer product accordingly. A preferred productform is to have the comonomer be present in the high molecular weightspecies of the total polymer composition to provide a favorable balanceof good film stretchability without breaking, coupled with lowextractables, low haze and good moisture barrier in the film.Accordingly in this preferred case, the same or lower levels of hydrogenare utilized during copolymerization as were used during polymerizationin the second or subsequent reactor.

[0083] For both polyethylene macromer product and branched polyolefinpreparation, it is known that many methods and permutations of theordering of addition of macromer and monomer species to the reactor arepossible, some more advantageous than others. For example, it is widelyknown in the art that preactivation of the metallocene with alumoxanebefore addition to a continuous solution-phase reactor yields higheractivities than continuous addition of metallocene and activator in twoseparate streams. Furthermore, it may be advantageous to controlprecontacting time to maximize catalyst effectiveness, e.g., avoidingexcessive aging of the activated catalyst composition.

[0084] It is preferable to use the polyethylene macromers such that theyare promptly functionalized or copolymerized after being prepared. Thehighly reactive vinyl groups appear to be susceptible to by-productreactions with adventitious impurities and, even, dimerization oraddition reactions with other unsaturated group-containing polymericchains. Thus maintaining in a cooled, inert environment afterpreparation and prompt subsequent use will optimize the effectiveness ofthe use of the polyethylene macromer product. A continuous processutilizing series reactors, or parallel reactors will thus be effective,the polyethylene macromer product being prepared in one and continuouslyintroduced into the other.

INDUSTRIAL UTILITY

[0085] The branched polyolefin polymers of the present invention exhibitimproved melt strength and shear thinning characteristics to standardpropylene copolymers. This results in improved processability of thepolymers, e.g. increased shear thinning and high output for a constantenergy input. These characteristics will result in improved processingin blow molding and thermoforming operations. For example, inthermoforming operations sag will be decreased and power consumptionwill be lowered in the extruders.

[0086] In order that the invention may be more readily understood,reference is made to the following examples, which are intended toillustrate the invention but not to limit the scope thereof.

EXAMPLES

[0087] General

[0088] All polymerizations were performed in a 2-liter Zipperclavereactor equipped with a water jacket for temperature control. Liquidswere measured into the reactor using calibrated sight glasses. Highpurity (>99.5%) toluene was purified by passing first through basicalumina activated at high temperature in nitrogen, followed by molecularsieve activated at high temperature in nitrogen. Polymerization gradeethylene was supplied directly in a nitrogen-jacketed line and usedwithout further purification. Propylene was purified by passing throughactivated basic alumina and molecular sieves. Methylalumoxane (MAO, 10%in toluene) was received from Albemarle Inc. in stainless steelcylinders, divided into 1-liter glass containers, and stored in alaboratory glove-box at ambient temperature.

[0089] For the polymer synthesis, propylene was measured into thereactor through a calibrated container. To ensure the reaction mediumwas well-mixed, a flat-paddle stirrer rotating at 750 rpm was used.

[0090] Reactor Preparation

[0091] The reactor was first cleaned by heating to 150° C. in toluene todissolve any polymer residues, then cooled and drained. Next, thereactor was heated using jacket water at 110° C. and the reactor waspurged with flowing nitrogen for a period of ˜30 minutes. Beforereaction, the reactor was further purged using 3 nitrogenpressurize/vent cycles (to 100 psi). The cycling served two purposes:(1) to thoroughly penetrate all dead ends such as pressure gauges topurge fugitive contaminants and (2) to pressure test the reactor.

[0092] Catalysts

[0093] All catalyst preparations were performed in an inert atmospherewith <1.5 ppm H₂O content. The catalyst system used in the synthesis ofmacromer was Cp₂ZrCl₂ activated with MAO. The catalyst systems used inthe synthesis of branched olefin copolymer were dimethylsilylbis(indenyl)hafnium dimethyl and dimethylsilyl bis(2-methyl indenyl)zirconium dichloride. The dimethylsilyl bis(indenyl)hafnium dimethyl wasactivated with [DMAH]⁺ [(C₆F₅)₄ B]⁻. The dimethylsilyl bis(2-methylindenyl) zirconium dichloride was activated with MAO. To maximizesolubility of the metallocene, toluene was used as a solvent. Thecatalyst was added to a stainless steel tube by pipette and transferredto the reactor.

[0094] Macromer Synthesis—General:

[0095] Ethylene was added to the reactor as needed to maintain totalsystem pressure at the reported levels (semi-batch operation). Ethyleneflow rate was monitored using a Matheson mass flow meter (model number8272-0424). To ensure the reaction medium was well-mixed, a flat-paddlestirrer rotating at 750 rpm was used.

Example 1

[0096] The reactor was simultaneously purged of nitrogen and pressuretested using two ethylene fill/purge cycles (to 300 psig). Then, thereactor pressure was raised to 40 psi to maintain positive reactorpressure during setup operations. Jacket water temperature was set to120° C. and 1200 milliliters of toluene were added to the reactor. Thestirrer was set to 750 rpm. Additional ethylene was added to maintain apositive reactor gauge pressure as gas phase ethylene was absorbed intosolution. The system was allowed to reach a steady temperature. Theethylene pressure regulator was next set to 40 psig and ethylene wasadded to the system until a steady state was achieved as measured byzero ethylene uptake. The reactor was isolated and a pulse of toluenepressurized to 300 psig was used to force the catalyst solution from theaddition tube into the reactor. The ethylene supply manifold wasimmediately opened to the reactor in order to maintain a constantreactor pressure as ethylene was consumed by reaction.

[0097] After 60 minutes of reaction, the reactor was isolated, cooled toroom temperature and methanol was added to precipitate the macromerproduct. The yield was 48 g. The polymer product had an Mn of 7,500 anda vinyl end group percentage of 73.

Example 2

[0098] The reactor was simultaneously purged of nitrogen and pressuretested using two ethylene fill/purge cycles (to 300 psig). Then, thereactor pressure was raised to ˜40 psi to maintain positive reactorpressure during setup operations. Jacket water temperature was set to120° C. and 1200 milliliters of toluene were added to the reactor. Thestirrer was set to 750 rpm. Additional ethylene was added to maintain apositive reactor gauge pressure as gas phase ethylene was absorbed intosolution. The system was allowed to reach a steady temperature. Theethylene pressure regulator was next set to 40 psig and ethylene wasadded to the system until a steady state was achieved as measured byzero ethylene uptake. The reactor was isolated and a pulse of toluenepressurized to 300 psig was used to force the catalyst solution from theaddition tube into the reactor. The ethylene supply manifold wasimmediately opened to the reactor in order to maintain a constantreactor pressure as ethylene was consumed by reaction.

[0099] After 20 minutes of reaction, the reactor was isolated, cooled toroom temperature and methanol was added to precipitate the macromerproduct. The yield was 23.3 g. The polymer product had an Mn of 4,300and a vinyl end group percentage of 73.

Example 3

[0100] A 2-liter reactor was charged with toluene (1 L), propylene (150mL), 10 g of the polyethylene macromer from Example 1 andTriisobutylaluminum (2.0 mL of 1M solution in toluene). The reactor washeated to 90° C. and equilibrated for 5 min. Then 2 mg of dimethylsilylbis(indenyl)hafnium dimethyl and 6 mg of [DMAH]⁺ [(C₆F₅)₄ B]⁻ in 5 mL oftoluene were injected using a catalyst tube. After 15 min, the reactorwas cooled to 25° C. and vented. The polymer was collected by filtrationand dried in air for 12 hours. Yield: 40 g.

Example 4

[0101] A 2-liter autoclave reactor was charged with toluene (1 L),propylene (150 mL), 10 g of the polyethylene macromer from Example 1 andTriisobutylaluminum (2.0 mL of 1 M solution in toluene). The reactor washeated to 90° C. and equilibrated for 5 min. Then 2 mg of dimethylsilylbis(2-methyl indenyl) zirconium dichloride activated in 5 mL of tolueneand 1 mL of MAO (10 wt % in toluene) was injected using a catalyst tube.After 15 min, the reactor was cooled to 25° C. and vented. The polymerwas collected by filtration and dried in air for 12 hours. Yield: 40 g.

Example 5

[0102] A 2-liter autoclave reactor was charged with toluene (1 L),propylene (150 mL), 10 g of the polyethylene macromer from Example 2 andTriisobutylaluminum (2.0 mL of 1M solution in toluene). The reactor washeated to 50° C. and equilibrated for 5 min. Then 2 mg of dimethylsilylbis(2-methyl indenyl) zirconium dichloride activated in 5 mL of tolueneand 1 mL of MAO (10 wt % in toluene) was injected using a catalyst tube.After 15 min, the reactor was cooled to 25° C. and vented. The polymerwas collected by filtration and dried in air for 12 hours. Yield: 53 g.

Example 6

[0103] A 2-liter autoclave reactor was charged with toluene (1 L),propylene (150 mL), 5 g of the polyethylene macromer from Example 2 andTriisobutylaluminum (2.0 mL of 1M solution in toluene). The reactor washeated to 50° C. and equilibrated for 5 min. Then 2 mg of dimethylsilylbis(2-methyl indenyl) zirconium dichloride activated in 5 mL of tolueneand 1 mL of MAO (10 wt % in toluene) was injected using a catalyst tube.After 15 min, the reactor was cooled to 25° C. and vented. The polymerwas collected by filtration and dried in air for 12 hours. Yield: 51 g.

Comparative Example 7

[0104] A 2-liter reactor was charged with toluene (1 L), propylene (150mL), and Triisobutylaluminum (2.0 mL of IM solution in toluene). Thereactor was heated to 50° C. and equilibrated for 5 min. Then 2 mg ofdimethylsilyl bis(2-methyl indenyl) zirconium dichloride activated in 5mL of toluene and 1 mL of MAO (10 wt % in toluene) was injected using acatalyst tube. After 15 min, the reactor was cooled to 25° C. andvented. The polymer was collected by filtration and dried in air for 12hours. Yield: 63 g.

[0105] Product Characterization

[0106] Some general characterization data for the polymers made in theExamples 3-6 and Comparative Example 7 are listed in Table 1. Thepolymer product samples were analyzed by gel permeation chromatographyusing a Waters 150C high temperature system equipped with a DRIDetector, Shodex AT-806MS column and operating at a system temperatureof 145° C. The solvent used was 1,2,4-trichlorobenzene, from whichpolymer sample solutions of 1.5 mg/ml concentration were prepared forinjection. The total solvent flow rate was 1 ml/minute and the injectionsize was 300 microliters. After elution of the polymer samples, theresulting chromatograms were analyzed using the Waters Expert Easeprogram to calculate the molecular weight distribution and one or moreof M_(n), M_(w) and M_(z) averages.

[0107] The melting point of the polymer product samples was determinedon a DSC 2910 Differential Scanning Calorimeter (TA Instruments). Thereported melting points were recorded at second melt with a temperatureramp of 10° C./min. “Wt. % C₂” indicates the percentage of polyethylenemacromer (C₂) incorporated into the polymer samples which was determinedby Analytical Composition Distribution analysis. TABLE 1 Physical DataSummary Example Mw MWD Tm (° C.) Wt. % C₂ 3 76,278 2.07 127 4 4 53,8442.37 148 9 5 164,394 4.62 147 10 6 138,267 3.78 149 3 Comp. 7 154,2671.68 149 0

Example 8

[0108] Quantification of long chain branching was performed using themethod of Randall, Rev. Macromol. Chem. Phys., C29, (2&3), p. 285-297.¹H-NMR analyses were performed using a 500 mHz Varian Unity modeloperating at 125° C. using d₂-tetrachloroethane as solvent. ¹³C-NMRanalyses were performed using at 100 mHz frequency, a Varian Unity Plusmodel under the same conditions.

[0109] Catalyst Preparation. A stainless steel catalyst addition tubewas prepared as outlined above. An aliquot of 1 milliliter of 10%methylalumoxane (MAO) solution in toluene was added, followed by 16 mgof Cp₂ZrCl₂ in toluene solution. The sealed tube was removed from theglovebox and connected to a reactor port under a continuous flow ofnitrogen. A flexible, stainless steel line from the reactor supplymanifold was connected to the other end of the addition tube under acontinuous flow of nitrogen.

[0110] Macromer Synthesis. The 1-liter reactor was simultaneously purgedof nitrogen and pressure tested using two ethylene fill/purge cycles (to300 psig (2170 kPa)). Then, the reactor pressure was raised to ˜20psig(239 kPa) to maintain positive reactor pressure during setupoperations. Jacket water temperature was set to 90° C. and 600milliliters of toluene were added to the reactor. The stirrer was set to750 rpm. Additional ethylene was added to maintain a positive reactorgauge pressure as gas phase ethylene was absorbed into solution. Thereactor temperature controller was set to 90° C. and the system wasallowed to reach steady state. The ethylene pressure regulator was nextset to 20 psig and ethylene was added to the system until a steady statewas achieved as measured by zero ethylene uptake. The reactor wasisolated and a pulse of toluene pressurized to 300 psig (2170 kPa) wasused to force the catalyst solution from the addition tube into thereactor. The 20 psig (239 kPa) ethylene supply manifold was immediatelyopened to the reactor in order to maintain a constant reactor pressureas ethylene was consumed by reaction. After 8 minutes of reaction, thereaction solution was quickly heated to 150° C. for 30 minutes to killthe catalyst, then cooled to 90° C. A small macromer sample was removedvia an addition port. Analysis by ¹³C-NMR indicated no measurable longchain branches were present in the macromer. The number and weightaverage molecular weights of the macromer were 9,268 and 23,587 Daltons,respectively, with 81.7% of olefins as vinyls.

[0111] Additional analysis was conducted on the polymer produced inExample 4 to determine the amount of branching and branch distribution.Since the ethylene contents at various molecular weight regions can bereadily determined by FTIR, it is possible to quantify the incorporationof macromer and calculate LCB distribution. Shown in FIG. 1 is theGPC-FTIR analysis for the polymer made in Example 4. The dots indicatethe ethylene content measured by FTIR at different molecular weightalong the GPC curve. Since the molecular weight (Mn) of the PE macromeris 7,500, the ethylene content detected at high molecular region clearlyindicates the incorporation of macromer in the PP backbones. Moreimportantly, it is possible to calculate the statisticalLCB-distribution (also shown in FIG. 1). Assuming that all macromershave the equal probability of incorporation (all macromers are equallyspaced along the PP backbones), then, the number of long chain branchesat certain molecular weight may be calculated according to the followingequation:

# of LCB/Chain =(MW of Polymer, DRI) (wt. fraction of PE)/(Mn ofMacromer) (1−wt. fraction of PE)

[0112]FIG. 2 shows a complex viscosity vs. shear rate curve for thepolymers produced in Example 5 and Comparative Example 7. Example 5demonstrates a steeper curve than Comparative Example 7. A steeper curvecorrelates to improved shear thinning performance as the viscosityreduces more rapidly at high shear rates. Therefore, the polymer productwhich was produced using macromers demonstrates improved processabilityover a polymer which was produced without the use of macromers.

[0113] While certain representative embodiments and details have beenshown for the purposes of illustrating the invention, it will beapparent to those skilled in the art that various changes in the processand products disclosed herein may be made without departing from thescope of the invention, which is defined in the appended claims.

We claim:
 1. A process for preparing a branched olefin copolymercomprising: (a) copolymerizing ethylene, optionally with one or morecopolymerizable monomers, in a polymerization reaction under conditionssufficient to form copolymer having greater than 40% chain end-groupunsaturation; (b) copolymerizing the product of a) with propyleneand,optionally, one or more copolymerizable monomers, in apolymerizationreactor under suitable polypropylenepolymerization conditions using achiral, stereorigid transition metal catalyst capable of producingisotactic polypropylene; and (c) recovering said branched olefincopolymer.
 2. The process of claim 1 wherein step a) is conducted by asolution process in which said ethylene and one or more copolymerizablemonomers are contacted with a transition metal olefin polymerizationcatalyst activated by an alumoxane cocatalyst, the mole ratio ofaluminum to transition metal is less than 220:1.
 3. The process of claim2 wherein step b) is conducted in a separate reaction by solution,slurry or gas phase polymerization.
 4. The process of claim 3 whereinsaid chiral, stereorigid transition metal catalyst compound in step b)is activated by an alumoxane cocatalyst or non-coordinating anionprecursor.